Question

pH	Fluorescence Counts
1	224
2	352
3	768
4	1312
5	352
6	192
7	128

Question 1

a) What pH would you recommend measurements of quinine sulfate in tonic water be taken at and why? What volume of 0.05M H2SO4 would be needed to be added to 100 ml volumetric flasks to give solutions at your chosen pH?

Hint: Estimate the magnitude of the error for a measurement if the pH of the solution was actually 4.5 when it is assumed to be 4.0?

b) Do you think that the pH of optimum signal is the most appropriate at which to do measurements?

Question 2

What are the absorption and emission maximum wavelengths of quinine in water?

Question 3

In table form show what volumes of 10,000 mg/L Cl-, 100 mg/L quinine sulfate and 0.05M sulfuric acid would need to be added to 100 mL volumetric flasks to produce a set of standards that contain 0, 50, 100, 300, 1000 and 2000 mg Cl-/L and 5 mg/L quinine sulfate at pH 3.

Answer 1

Solution :- Part a)

pH 4  would be recommend measurements of quinine sulfate in tonic water .Because when the maximum number of fluorescent counts can be detected.

So pH= -log[H3O+]

For pH=4

4=-log(H3O+)

So Concentration Of H3O+= 0.0001

0.05M H2SO4 || 0.1M H+

a 0.05 M solution of H2SO4 was prepared according to the following calculation:

C1V1=C2V2

0.0001X 100ML = O.1 X x = 0.1 mL

Ans :- Part b)

Yes,pH of optimal signal is the most measurement of the quinine sulfate in tonic water.